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Quasi-Maximum Likelihood Estimators in Generalized Linear Models with Autoregressive Processes

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Acta Mathematica Sinica,English Series 2014年第12期30卷 2085-2102页

作者： hong chang hU Lei SONG School of Mathematics and Statistics Hubei Normal University Educational Research Institute

the paper studies a generalized linear model（GLM）yt = h（xt^t β）＋ εt,t = l,2,...,n,where ε1 = η1,ε1 =ρεt ＋ηt,t = 2,3,...;n,h is a continuous differentiable function,ηt＇s are independent and identically distributed random errors with zero mean and finite variance σ^***,the quasi-maximum likelihood（QML） estimators of β,p and σ^2 are ***,under mild conditions,the asymptotic properties（including the existence,weak consistency and asymptotic distribution） of the QML estimators are ***,the validity of method is illuminated by a simulation example.

关键词： Generalized linear model quasi-maximum likelihood estimator autoregressive processes weak consistency asymptotic distribution

Simulating global soil-CO_2 flux and its response to climate change

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Journal of Environmental Sciences 2000年第3期12卷 257-265页

作者： PENG chang-hui Michael JApps Ontario Forest Research Institute Ministry of Natural Resources1235 Queen Street EastSault Ste.MarieON P6A 2E5Canada. Morthern Forestry Center Canadian Forest Service5320-122 StreetEdmontonAlberta T6H3S5 Canada

It has been argued that increased soil respiration would become a major atmospheric source of CO\-2 in the event of global warming. the simple statistical models were developed based on a georeferenced database with 0 5°×0 5° longitude/latitude resolution to simulate global soil\|CO\-2 fluxes, to investigate climatic effects on these fluxes using sensitivity experiments, and to assess possible responses of soil\|CO\-2 fluxes to various climate change scenarios. the statistical models yield a value of 69 PgC/a of global soil\|CO\-2 fluxes for current condition. Sensitivity experiments confirm that the fluxes are responsive to changes in temperature, precipitation and actual evapotranspiration, but increases in temperature and actual evapotranspiration affect soil\|CO 2 fluxes more than increases in precipitation. Using climatic change projections from four global circulation models, each corresponding to an equilibrium doubling of CO 2, it can be found that the largest increases in soil\|CO 2 fluxes were associated with the boreal and tundra regions. the globally averaged soil\|CO 2 fluxes were estimated to increase by about 35% above current values, providing a positive feedback to the greenhouse effect.

关键词： climatic variable sensitivity experiment soil respiration statistical model

Differential effects of atrial and brain natriuretic peptides on human pulmonary artery:An in vitro study

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World Journal of Cardiology 2019年第10期11卷 236-243页

作者： Azar hussain Robert t Bennett Zaheer tahir Emmanuel isaac Mubarak A Chaudhry Syed S Qadri Mahmoud Loubani Alyn h Morice Department of Cardiothoracic Surgery Castle Hill HospitalCottingham HU165JQUnited Kingdom Centre for Cardiovascular and Metabolic Research Hull York Medical SchoolCastle Hill HospitalCottingham HU165JQUnited Kingdom

BACKGROUND the prevalence of cardiovascular diseases,especially heart failure,continues to rise *** heart failure,increasing levels of circulating atrial natriuretic peptide(ANP)and brain natriuretic peptide(BNP)are associated with a worsening of heart failure and a poor *** to test whether a high concentration of BNP would inhibit relaxation to *** Pulmonary arteries were dissected from disease-free areas of lung resection,as well as pulmonary artery rings of internal diameter 2.5–3.5 mm and 2 mm long,were *** artery rings were mounted in a multiwire myograph,and a basal tension of 1.61gf was *** equilibration for 60 min,rings were pre-constricted with 11.21μmol/L PGF2α(EC80),and concentration response curves were constructed to vasodilators by cumulative addition to the myograph *** Although both ANP and BNP were found to vasodilate the pulmonary vessels,ANP is more potent than ***50 of ANP and BNP were 8.96±0.21 and 7.54±0.18,respectively,and the maximum efficacy(Emax)for ANP and BNP was-2.03 gf and-0.24 gf,*** addition of BNP,the Emax of ANP reduced from-0.96gf to-0.675gf(P=0.28).CONCLUSION BNP could be acting as a partial agonist in small human pulmonary arteries,and inhibits relaxation to *** levels of circulating BNP could be responsible for the worsening of decompensated heart *** finding could also explain the disappointing results seen in clinical trials of ANP and BNP analogues for the treatment of heart failure.

关键词： heart failure Atrial natriuretic peptide Brain natriuretic peptide In-vitro humans

Photolysis of hexamethylenediaminetetra(methylenephosphonic acid)(hDtMP)using manganese and hydrogen peroxide

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Emerging Contaminants 2020年第1期6卷 10-19页

作者： Ramona Kuhn isaac Mbir Bryant Robert Jensch Stephan Liebsch Marion Martienssen Brandenburg University of technology Cottbus-Senftenberg Institute of Environmental Technology and Process EngineeringChair of Biotechnology of Water Treatment03046CottbusGermany University of Cape Coast Department of Environmental ScienceCape CoastGhana Zschimmer&Schwarz Mohsdorf Gmbh&Co KG Chemnitztalstr.109217BurgstoadtGermany

Aminophosphonates such as hexamethylenediaminetreta(methylene phosphonic acid)(hDtMP)are categorised as persistent *** are commonly used as scale inhibitors in cooling water systems and desalination *** utilisation,they are often discharged into aquatic environment without *** oxidation processes(AOP)are promising pre-treatments for industrial wastewater *** investigated the photodegradation of hDtMP with or without addition of manganese(Mn2t)and/or *** to results of our former photodegradation studies,we found that hDtMP also undergoes conversion with or without additives during the ultra violet(UV)*** reaction rate was most affected by the addition of h2O2,*** hDtMP degradation was accelerated by a factor 3.85 compared with UV treatment without *** addition of Mn2t accelerated the degradation of hDtMP only by a factor 1.53 compared with the UV treatment without *** combined addition of Mn2t and h2O2 accelerated the hDtMP degradation by a factor ***,the initial cleavage is not initiated as expected at the CeN bond but at the CeP bond of the methyl carbon and the phosphorus of the methylenephosphonic acid group of *** initial cleavage was independent whether the UV treatment was performed with or without ***,we conclude that the degradation mechanism is similar independent of the four tested treatment *** identified amino(methylenephosphonic acid)AMPA,dimethylamino(methylenephosphonic acid)DAMP and iminodi(methylenephosphonic acid)IDMP as the major breakdown products by performing LC/MS *** major mineralisation products were ortho-phosphate,ammonium and carbon *** mass balances of unknown breakdown products allowed us to speculate about the molecular size of the unknown organic breakdown products.

关键词： hDtMP hydrogen peroxide Manganese LC/MS Phosphonates Photolysis

Critical Exponent for the Parabolic Equation u_t=Δu^m + h(t)u^p in a Cone

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Acta Mathematica Sinica,English Series 2012年第8期28卷 1623-1632页

作者： chang Chun LIU Song Zhe LIAN Department of Mathematics Jilin University

In this paper, we study the initial-boundary value problem of porous medium equationut = △um ＋ h（t）up in a cone D = （0, ） Ω, where h（t） - t. Let wl denote the smallest Dirichlet eigenvalue for the Laplace-Beltrami operator on Ω and let l denote the positive root cf l2＋（n-2）l = wl. 2（＋1）＋（rn- 1）, then the problem has no global nonnegative solutions We prove that if m 〈 p 〈 m ＋ for any nonnegative u0 unless u0 -= 0; if p 〉 m ＋＋ a（m - 1）, then the problem has global n4-1 solutions for some uo 〉 O.

关键词： Porous medium equation cone critical exponent

Neutronics analysis of a subcritical blanket system driven by a gas dynamic trap-based fusion neutron source for ^(99)Mo production

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Nuclear Science and techniques 2023年第4期34卷 14-25页

作者： hou-hua Xiong Qiu-Sun Zeng Yun-Cheng han Lei Ren isaac Kwasi Baidoo Ni Chen Zheng-Kui Zeng Xiao-Yu Wang School of Nuclear technology and Chemistry&Biology and hubei Key Laboratory of Radiation Chemistry and Functional Materials Hubei University of Science and TechnologyXianning 437100China Institute of Nuclear Energy Safety technology Hefei Institutes of Physical ScienceChinese Academy of SciencesHefei 230031China Nuclear Reactors Research Centre National Nuclear Research InstituteGhana Atomic Energy CommissionBox LG 80Legon-AccraGhana teaching and Research Section of Nuclear Medicine School of Basic Medical SciencesHefei Institutes of Physical ScienceAnhui Medical UniversityHefei 230031China

Gamma-emitting radionuclide ^(99m)tc is globally used for the diagnosis of various pathological conditions owing to its ideal single-photon emission computed tomography (SPECt) ***,the short half-life of ^(99m)tc (t_(1/2)=6 h)makes it difficult to store or ***,the production of ^(99m)tc is tied to its parent radionuclide ^(99)Mo (t_(1/2)=66 h).the major production paths are based on accelerators and research *** reactor process presents the potential for nuclear proliferation owing to its use of highly enriched uranium (hEU).Accelerator-based methods tend to use deuterium–tritium(D–t) neutron sources but are hindered by the high cost of tritium and its challenging *** this study,a new ^(99)Mo production design was developed based on a deuterium–deuterium (D–D) gas dynamic trap fusion neutron source (GDt-FNS) and a subcritical blanket system (SBS) assembly with a low-enriched uranium (LEU) ***-FNS can provide a relatively high-neutron intensity,which is one of the advantages of ^(99)Mo *** provide a Monte Carlo-based neutronics analysis covering the calculation of the subcritical multiplication factor (k_(s)) of the SBS,optimization design for the reflector,shielding layer,and ^(99)Mo production *** calculations,including the neutron flux and nuclear heating distributions,are also provided for an overall evaluation of the production *** results demonstrated that the SBS meets the nuclear critical safety design requirement (k_(s)tained a high ^(99)Mo production *** proposed system can generate approximately 157 Ci ^(99)Mo for a stable 24 h operation with a neutron intensity of 1×10^(14) n/s,which can meet 50%of China’s demand in 2025.

关键词： Gas dynamic trap Fusion neutron source Molybdenum-99 Low-enriched uranium Subcritical blanket system

Dislocation density-me diate d creep ageing behavior of an Al-Cu-Li alloy

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Journal of Materials Science & technology 2024年第7期174卷 204-217页

作者： chang Zhou Lihua Zhan Chunhui Liu Minghui huang College of Mechanical and Electrical Engineering Central South UniversityChangsha 410083China State Key Laboratory of Precision Manufacturing for Extreme Service Performance Central South UniversityChangsha 410083China Light Alloys Research Institute Central South UniversityChangsha 410083China

Creep aging is well-known to be a time-dependent,coupled process of deformation and precipitation strengthening for age-hardening *** existing mechanisms are mainly attributed to those interac-tions between atomic diffusion and dislocation ***,an understanding of the relationship between dislocation density and a special multistage creep behavior,i.e.,double steady creep feature,is still far *** we investigate the effect of various dislocation density levels on such an abnormal multistage creep of an Al-Cu-Li *** find that the increased dislocation densities enable an apparent time decrease(from 6.2 h to 0.8 h)of their first steadyⅡ-*** yield strength of post-aged sam-ples increases from 425.0 MPa to 580.0 MPa while the corresponding elongation decreases from 12.3%to 7.3%for the creep-aged samples#1 to#*** results also reveal that a great difference in dislocation configuration,tailored by various density levels,results in varying creep processes of theⅡ-*** stage is closely related to the nucleation and early growth of t_(1)*** number densities(maximum:2.9×10^(19)m^(-3))and the average length(maximum:21.3 nm)of t_(1)precipitates are much smaller than those of the stable peak-aged t_(1)phases,suggesting that creepⅡ-stage of all three creep-aged samples is dominant by the nucleation and initial growth of those t_(1)*** study provides valuable insights into the dislocation density-mediated creep deformation of an Al-Cu-Li alloy.

关键词： Dislocation density Al-Cu-Li alloy Creep ageing t_(1)precipitation

Fabrication of a nano-sized ZSM-5 zeolite with intercrystalline mesopores for conversion of methanol to gasoline

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Journal of Energy Chemistry 2017年第1期26卷 139-146页

作者： tingjun Fu Jiangwei chang Juan Shao Zhong Li Key Laboratory of Coal Science and technology Ministry of Education and Shanxi ProvinceTaiyuan University of TechnologyTaiyuan 030024ShanxiChina

Carbon deposition during methanol to hydrocarbons leads to the quick deactivation of ZSM-5 catalyst and it is one of the major problems for this technology. Decreasing the crystal size or introducing mesopores into ZSM-5 zeolites can improve its diffusion property and decrease the coke formation. In this paper, nano-sized ZSM-5 zeolite with intercrystalline mesopores combining the mesoporous and nano sized structure was fabricated. For comparison, the mesoporous ZSM-5 and nano-sized ZSM-5 were also prepared. these catalyst samples were characterized by XRD, BEt, Nh3-tPD, tEM, Py-IR and tG techniques and used on the conversion of methanol to gasoline in a fixed-bed reactor at t=405 degrees C, WhSV =4.74 h(-1) and P=1.0 MPa. It was found that the external surface area of the nano-sized ZSM-5 zeolite with intercrystalline mesopores reached 104 m(2)/g, larger than that of mesoporous ZSM-5 (66 m(2)/g) and nano sized ZSM-5 (76 m(2)/g). Catalytic lifetime of the nano-sized ZSM-5 zeolite with intercrystalline mesopores was 93 h, which was only longer than that of mesoporous ZSM-5 (86 h), but shorter than that of nano sized ZSM-5 (104 h). Strong acidity promoted the coke formation and thus decreased the catalytic lifetime of the nano-sized ZSM-5 zeolite with intercrystalline mesopores though it presented large external surface that could improve the diffusion property. the special zeolite catalyst was further dealuminated to decrease the strong acidity. After this, its coke formation rate was slowed and catalytic lifetime was prolonged to 106 h because of the large external surface area and decreased weak acidity. this special structural zeolite is a potential catalyst for methanol to gasoline reaction. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.

关键词： ZSM-5 Crystal size Mesopore Acidity Methanol to gasoline

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串联微柱在超临界流体色谱中的应用

色谱 1992年第3期10卷 155-157页

作者：马熙中 h-C.Karen chang L.t.taylor 北京化工学院应用化学系 Department of Chemistry Virginia Polytechniv Insititute and State UniversityBlacksburgVA 24061USA

得力于气相和液相色谱的进步,一种新的色谱技术,超临界流体色谱(SFC)异军突起,而各种柱技术又推动了这种技术的发展速度。在SFC中开管柱和填充柱都在使用,且各具特色。但除了单位柱长具有较大的压降、柱子使用长度受到限制外,填充柱显... 详细信息

得力于气相和液相色谱的进步,一种新的色谱技术,超临界流体色谱(SFC)异军突起,而各种柱技术又推动了这种技术的发展速度。在SFC中开管柱和填充柱都在使用,且各具特色。但除了单位柱长具有较大的压降、柱子使用长度受到限制外,填充柱显示出更多的优点。微柱,即填充石英毛细管柱,内径小于1mm。它以弹性石英毛细管作为柱管,管内填充色谱填料。

关键词：串联微柱超临界流体色谱